1. Field of the Invention
The present invention relates to a leather-like sheet which has writing (handwriting effect), a high-quality external appearance, and soft hand touch and feel similar to that of natural leather, which has excellent lasting ability in shoemaking and shape-keeping ability after shoemaking. The leather-like sheet has, if necessary, both waterproofness and moisture permeability, and the waterproofness is hardly damaged when an external factor, such as external stress by stretching, scratching, patting or the like, is applied thereto, or in the case that stains and the like adhere thereon. Thus, the leather-like sheet is useful for making to shoes and related articles. The present invention also relates to shoes produced from the leather-like sheet.
2. Description of the Background
Recently, in view of the importance attached to outdoor activity, such as recreation, the use of natural leather suede, natural leather nubuck, suede-like materials and nubuck-like materials, which exhibit casual feeling, is becoming more frequent in the fashion field of shoes. For conventional nubuck-like artificial leather, however, a fiber having a larger fineness is used instead of the collagen fiber which makes actual natural leather nubuck. The conventional nubuck-like artificial leather has a poor external appearance and a rough feel, and thus does not provide a high-quality appearance. When fiber making produces artificial leather having uniform fineness over its whole layers, such fine folds as found in natural leather has cannot be formed. In the case that artificial leather is composed of fibers having different finenesses, the same fact is true because of the mixture of these fibers.
In the case that a napped surface layer is composed of a mixture of a microfine fiber having a fineness of 0.5 denier or less and a fiber having a thickness 4 times larger than that of the microfiber, as described in, for example, Japanese Patent Application Laid-Open No. 59-1749, the leather has a rough feel because of the fibers having different thicknesses. In the case that the leather is dyed, the unevenness of dyeing concentration is easily generated because of the different thicknesses of the fibers. Therefore, the leather does not have a high-quality external appearance. In the case of putting a fiber-entangling web composed of a microfine fiber upon a woven fabric and then integrating them with a needle punch, as described in Japanese Patent Application Laid-Open No. 3-137281, the same problem arises. This is because the fiber, of the woven fabric, having a large fineness is present in its surface or near it.
As an example wherein layers composed of fibers having different thicknesses are stacked and these fibers are not intermixed, Japanese Patent Application Laid-Open No. 59-116477 discloses a technique wherein a woven fabric or knitted fabric is affixed onto an artificial leather composed of a fiber having a fineness of I denier or less and an elastic polymer with an adhesive agent applied in the form of spots. In this technique, however, the affixed layer is the woven fabric or knitted fabric and the thickness of the fiber making it is too large. It can therefore enhance, as a liner material, the strength of the artificial leather, but at the time of lasting in a shoemaking step, unevenness of the woven fabric or knitted fabric is reflected on the surface of the shoes. Alternatively, in accordance with rupture elongation of the woven fabric or knitted fabric, this technique may be unsuitable for the lasting step. Thus, the sorts of shoes to which the technique may be applied are limited.
In many conventional artificial leathers, the whole layers are dyed. Thus, there arises a problem that in the case of using the artificial leathers particularly in shoes, socks and the like may be polluted by their dye in accordance with color fastness of a portion which contacts a foot, i.e., the back face of the leather-like sheets.
In connection with waterproofness, nubuck-like materials do not have any grain layer as a surface layer in same manner as natural leather nubuck. Therefore, when the nubuck-like materials are used in shoes, they do not easily become musty because of larger moisture permeability. Thus, they have an advantage that when a person wears such shoes, the person has a good feeling. On the other hand, the nubuck-like materials have a disadvantage that rainwater permeates through a layer thereof to penetrate very easily into the inside. As a manner for solving this drawback, there is proposed, for example, a method of disposing a waterproof layer onto the back surface of the layer. Such a method has a problem that since the waterproof layer is exposed as a back surface, the waterproof layer is damaged in the case of applying external stress factors such as stretching, writing and padding powers to the back surface.
The Inventors have investigated nubuck-like sheets which have the hand touch and feel like natural leather, and both lasting ability upon shoemaking and shape-keeping ability, and has, if desired both of waterproofness and moisture permeability, these performances not being damaged by external factors. As this investigation, the Inventors have found that the above-mentioned object can be attained by the following leather-like sheet, and thus have made the present invention: a leather-like sheet wherein the following fiber-entangled nonwoven fabrics (A) and (B) are stacked with an adhesive agent present in a discontinuous state:
(A) is a fiber-entangled nonwoven fabric containing an elastic polymer and comprising a microfine fiber (a) having a fineness of 0.1 denier or less, wherein the surface which is opposite to the surface which is on fabric (B) is fluffed, and having rupture elongations in the longitudinal and latitudinal directions of 50% or more and 80% or more, respectively, and
(B) is a fiber-entangled nonwoven fabric containing an elastic polymer and comprising a microfine fiber (b) having a fineness of 0.5 denier or less, the fineness being 4 times or more larger than that of the fiber (a), and having rupture elongations in the longitudinal and latitudinal directions of 50% or more and 80% or more, respectively.
In the present invention, preferably the fiber-entangled nonwoven fabric (A) is dyed and the fiber-entangled nonwoven fabric (B) is not substantially dyed. Optionally, a film layer (C) comprising an elastic polymer and having moisture permeability is between the fiber-entangled nonwoven fabrics (A) and (B). The present invention also relates to a method for producing the sheet. Further, the invention also relates to shoes obtainable by subjecting the above-mentioned leather-like sheet to lasting shoemaking.
Natural leather has, beneath its surface layer comprising a bundle of microfine fibers, a layer comprising slightly thicker fibers than the microfine fibers. Without being limited to any particular theory, it is presumed that the leather-like sheet of the present invention has a sectional structure similar to such a sectional structure of the natural leather and this fact gives hand touch, feel, folds, etc., like those of the natural leather to the leather-like sheet of the present invention.